Someone who would say anything to get a highest-rated comment on a YouTube video. Most of the time the comment has nothing to do with the video or at times the person would post a paragraph-long comment just so their comment can be noticed. A thumb whore would use certain techniques to get people's attention like abuse the caps lock button.

Thumb whore- "The quality of this video sucks! Stop recording shit with a cellphone and get a real camera! Thumbs up if you agree!!!"
or
Thumb whore- "THIS SONG ROCKS!!! THUMBS UP IF YOU AGREE!!"

One who shamelessly either thumbs up their down definitions day after day, or thumbs down definitions of things that they dont like. The same demographic who used to request for deletion any definitions they found "offensive"....

I clicked on that authors name and jeez, what a thumb whore, he has like 20 thumbs up on the word "ashjgihjaoifsghjafngj"